When to stick a fork in it?

I've spent the past week (in between teaching English 101, Science Fiction, Beowulf and Old Norse) doing revisions on How Tradition Works. Part of this process has been reading new books suggested by my outside reviewers. Some of these have proven helpful, some less so.
My question is: when do you just say "stick a fork in it, it's done?" I finished HTW in April, revised it in August, and then got reader's reports back in December and January. But really the bulk of the reading and research was done when I was on research leave in 2001. Since then there has been a lot of important scholarship that has come out. But I can't completely re-write HTW each time I read a new book on Memes or on the 10th century. It's frustrating. For example, I just read Religion Explained by Pascal Boyer. Brilliant argument. Only tangentially related to my book, but I wonder if I should go through HTW and at least reference each time Boyer's argument might be useful or connected or (my favorite) "not incompatible" with my thesis.

Any writers out there have good rules of thumb for deciding when to stop and just include all the new scholarship in the sequel?

Sorry about the lack of posting since I received my tenure. It's been a busy week or so. We were interviewing job candidates WThF (all excellent people, which was nice, though it makes the actual decision difficult) and then I was "single-dad" for a week while my wife made the world slightly safer for democracy, and our semester started up at the same time.

But the big news is that my book of my own research, How Tradition Works: A Descriptive Cultural Poetics of the Anglo-Saxon Tenth Century received its second favorable reader's report. So it looks like it will be published, but I am in the throes of revisions.

For my family members and non-academic readers, let me explain how this process works. An academic press has procedures in place to try to keep things on the level: books shouldn't be published because you're a drinking buddy of the editor-in-chief, etc. So presses get external, anonymous reviewers to go over a manuscript and recommend whether or not it should be published. Both of my outside reviewers said "publish," and the ed-in-chief of the press seems to have liked the book before he sent it out, so I am much of the way to publication. I now have to do the revisions that the readers suggested (or decide that they're bad revisions, but more than 90% of them are in fact good), then write a letter to the Board of Directors of the press, explaining what I did and why (i.e., I took these pieces of advice, but I thought this was wrong because...). Then the Ed-in-Chief and the Board meet and decided whether to offer me a contract. This isn't a done deal, but with two very strong reader's reports, my willingness to actually make the changes (i.e., sometimes you are asked to make changes that you just don't want to agree to), and the Ed-in-chief already having read the book, things look very good.

And I got the news on the Friday after I got tenure, so it was a big week.

Once I have a book contract in hand, I'll say who is going to publish How Tradition Works, though you can figure it out if you read through my site.

With the publication of How Tradition Works, Beowulf and the Critics and the big articles coming out on the Old English translation of the Rule of Chrodegang (JEGP) and on the Anglo-Saxon wills (SELIM), I'll be in good shape to focus my attention on getting the first issue of Tolkien Studies edited and printed by May 1 and getting my essay collection, Anglo-Saxon Poetry in its Tenth-Century Context in shape to give to a press [hear that, contributors, I have three essays; I need the other four so I can edit over Spring Break in March]. Maybe I can get enough done so that I can spend part of the summer painting my house....